Algae-based bioplastics are gaining considerable attention due to their eco-friendly and sustainable characteristics. The production of these bioplastics involves several steps, including cultivation, harvesting, and processing of algae. Among these, the harvesting step is one of the most critical and challenging stages. It involves the separation of algae from the culture medium, which is primarily water. One of the efficient techniques used for this purpose is centrifugation.
Centrifugation is a mechanical process that uses centrifugal force to separate particles from a solution according to their size, shape, density, viscosity of the medium, and rotor speed. In the context of algal biomass harvesting, centrifugation separates microalgae cells from the aqueous media by spinning the mixture at high speed. This process forces the denser algae cells to migrate away from the axis of rotation and settle at the bottom of the centrifuge tube.
The efficiency of centrifugation in algae harvesting depends on various factors such as the type and size of algae, centrifugal force applied, temperature, pH level, and duration of centrifugation. For instance, smaller algae species require higher centrifugal forces for effective harvesting.
There are different types of centrifuges used for algae harvesting such as disc stack centrifuges, decanter centrifuges, and tubular bowl centrifuges. Disc stack centrifuges are commonly used for small-scale algae harvesting due to their high-speed operation and ability to handle large volumes. Decanter centrifuges are typically used for large-scale operations because they can handle high solid concentrations and offer continuous operation.
Once harvested through centrifugation, the algal biomass undergoes various processing techniques to convert it into bioplastic. The first step in this process is usually drying to reduce the moisture content in the biomass. This can be achieved through sun drying, oven drying or freeze-drying.
The dried algal biomass is then subjected to pyrolysis or hydrothermal liquefaction to break down the complex organic molecules into simpler ones. These simplified molecules can then be polymerized through processes like fermentation or chemical synthesis to form bioplastics.
Producing bioplastics from algae offers several advantages over traditional petroleum-based plastics. Firstly, they are renewable and biodegradable, reducing environmental pollution significantly. Secondly, algae can be cultivated in non-arable lands using wastewater or seawater without competing with food crops for resources.
However, challenges exist in scaling up the production of algae-based bioplastics due to high energy requirements in cultivation and harvesting stages. In particular, the energy-intensive nature of centrifugation has prompted researchers to explore other cost-effective and energy-efficient harvesting methods such as flocculation and filtration.
In conclusion, while there are challenges associated with energy consumption and scalability, centrifugation presents an efficient method for harvesting algae for bioplastic production. As research continues in this field, it is hoped that optimizations in these techniques will make algae-based bioplastics a more viable option in our pursuit towards a more sustainable future.